aggiunto filtro per conferenza e select-related per limitare le query
aggiunto filtro per conferenza e select-related per limitare le query

malemburg/epcon,matrixise/epcon,pythonitalia/assopy,EuroPython/epcon,EuroPython/epcon,matrixise/epcon,matrixise/epcon,malemburg/epcon,PythonSanSebastian/epcon,barrachri/epcon,PythonSanSebastian/epcon,malemburg/epcon,barrachri/epcon,EuroPython/epcon,PythonSanSebastian/epcon,barrachri/epcon,barrachri/epcon,pythonitalia/assopy,malemburg/epcon,artcz/epcon,barrachri/epcon,PythonSanSebastian/epcon,artcz/epcon,artcz/epcon,matrixise/epcon,artcz/epcon,malemburg/epcon,malemburg/epcon,PythonSanSebastian/epcon,matrixise/epcon,PythonSanSebastian/epcon,matrixise/epcon,artcz/epcon,barrachri/epcon,artcz/epcon,EuroPython/epcon